1. Field of the Invention
This invention is concerned with the activation of ferrierite for the catalytic conversion of hydrocarbons. More particularly, it is concerned with methods for activating ferrierite in a way that makes it selective for cracking normal paraffins and controllable amounts of branched paraffins.
2. Discussion of the Prior Art
It is well known in the prior art that certain zeolites including those designated by the Linde Division of Union Carbide Corporation by the letters X, Y, A and L and the naturally occurring crystalline zeolites, chabazite, erionite, faujasite and mordenite, can be treated by steps comprising heating and ion exchange. For example, U.S. Pat. No. 3,402,996 is concerned with a method of cation exchanging these and other zeolites, the method comprising a conventional ion exchange step, a calcination step at 400.degree. to 1500.degree. F and an additional conventional ion exchange step.
U.S. Pat. No. 3,375,065 discloses a method of producing a thermally stable synthetic faujasite containing less than 1% Na.sub.2 O by (1) exchanging the faujasite with ammonium cations, heating the exchanged product above 350.degree. F, exchanging again with ammonium cations and finally exchanging with magnesium or rare earth or mixtures thereof. Stability of the faujasite is attained by reducing the concentration of the ammonium ion.
In one of its aspects, U.S. Pat. No. 3,354,077 teaches that an ammonium Y crystal-type zeolite can be heated at 300.degree.-700.degree. F in an atmosphere containing water vapor without destruction of crystallinity; stabilization of this zeolite is completed by continuing the heating up to about 1200.degree. F in a water vapor atmosphere.